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- volume 13 (2010)
- number 3
- High-frequency cycles and their sequence stratigraphic context: orbital forcing and tectonic controls on Devonian cyclicity, Belgium (The André Dumont medallist lecture)
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High-frequency cycles and their sequence stratigraphic context: orbital forcing and tectonic controls on Devonian cyclicity, Belgium (The André Dumont medallist lecture)
Abstract
The sequence stratigraphic approach has evolved into an important tool for stratigraphic analysis and does have an element of prediction. Several sequence models have been proposed and are in use, but there have been emotive discussions in the literature over these, as well as systems tracts and key surfaces. Metre-scale cycles (parasequences) are the building blocks of sequences and are an essential component of carbonate successions throughout the stratigraphic record. Their thickness and facies patterns, reflecting the longer-term changes in accommodation that affected deposition, enable the various systems tracts in a sequence to be recognised. There have been many arguments over the origin of parasequences with orbital forcing, tectonic and sedimentary mechanisms all having their proponents. Devonian carbonates of the Ardennes-Eifel-Aachen area are dominated by a suite of parasequence types deposited in ramp and shelf-interior locations. They show thickness patterns and trends in facies, which on a broad scale can be correlated across the region, whereas individual cycles cannot. Some packaging of cycles is seen, which could indicate an orbital-forcing control. However, there is clear evidence for a tectonic control on regional thickness patterns in some parts of the succession, as a result of deposition across syn-sedimentary extensional faults. As with many areas of Earth Science, explanation involves a combination of several hypotheses and here one mechanism does not seem to have been responsible for the Devonian cyclicity.
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A propos de : Maurice TUCKER
Department of Earth Sciences, Durham University, Durham DH1 3LE (England). E-mail: m.e.tucker@durham.ac.uk
A propos de : Joanna GARLAND
Cambridge Carbonates Ltd, Northampton House, Poplar Road, Solihull, West Midlands, B91 3AP (England). E-mail: jogarland@cambridgecarbonates.co.uk